The present invention relates to a frequency multiplier of the type used for telecommunications by millimeter waves for obtaining a very high stability, ultra-high frequency signal source.
The realisation of millimeter wave radio links requires phase-locked ultra-high frequency sources able to supply a few dozen milliwatts, which are capable of being frequency modulated and which are able to function correctly in the temperature range -30.degree. to +70.degree. C. It is known to realise such sources at frequencies of approximately 4 GHz, but not with frequencies of approximately 40 GHz by means of an oscillator operating correctly at said frequency. Thus, one known procedure is e.g. of combining a frequency multiplier which multiplies the frequency by 10 with a phase-locked 4 GHz signal source in order to obtain a phase-locked 40 GHz signal. This process makes it possible to obtain a much better frequency stability than that of e.g. a Gunn diode oscillator, operating directly at the frequency of 40 GHz.
It is known to realise a multiplier capable of multiplying a frequency by 10, which receives an incident signal of frequency 4 GHz and supplying an output signal of frequency 40 GHz by means of an avalance semiconductor diode for frequency multiplaction, by applying the incident signal to the diode via an impedance matching low pass filter thus preventing the rise of harmonic frequencies towards the source of the incident signal and by collecting the tenth harmonic generated by the diode by means of a fixed tuned cavity containing the diode, the latter having a regulatable position within the cavity in order to obtain the operation giving the best efficiency. The impedance matching low pass filter generally comprises a transformer, whose very difficult control must be adjusted for each multiplier. The efficiency obtained with the known devices incorporating an avalance diode is approximately 5%, whereas in the case of a step-receovery diode it is 1% or 2%. The object of the invention is to obviate this low efficiency, while reducing to the minimum the number of controls to be carried out on the multiplier.